(a) Field of the Invention
This invention relates to a system and a process for treating influent waste water and more particularly, but not by way of limitation, to an electrocoagulation waste water batch tank treatment system and process for greatly reducing various types of contaminates held in suspension in the waste water.
(b) Discussion of Prior Art
The evolution of electrocoagulation is driven by a need to make waste water treatment processes more efficient. Recent increases in electrical costs and metal have changed the goals from optimum treatment efficiency to reduced operating costs. Many of the exotic configurations requiring specific electrode materials have given way to trying to utilize available stock material. New ideas have helped reduce electrode costs, but still there is a need for a more versatile, more flexible, standard design using inexpensive materials and components. The subject invention disclosed herein attempts to reduce system materials and components to a lowest common denominator.
Heretofore, previous “flow-through” and “static” water treatment processes have had flaws that prevented them from being viable treatments for large, complex and variable waste streams. A particular flaw was the scaling and plugging of electrodes, which plagued the treatment process as the waste water stream changed in composition. It is possible to develop a treatment scheme that will not plug the electrodes if the composition of the stream remained relatively consistent, but not if the composition varies. Efforts to install elaborate monitoring and control systems have failed when waste stream contaminants coated or blinded sensors, thus rendering the system controls useless. Other methods have been employed to prevent scaling and plugging of the electrodes including polarity reversing and other processing aids. But these methods have proven to be unreliable.
Methods for increasing dwell time for contaminated water in electrode modules and the surface area of the electrodes have been tried by increasing the number of electrode plates in the module or increase the number of modules. But, these optional methods increase the pumping pressure of the water necessary to push the fluid through the electrode modules. The increased water pressure causes extra strain on electrode module gaskets and if the pressure is high enough, leaks and failure of the module may occur. Additionally, in these cases, there is little or no chance for the precipitate to develop or coagulate into bigger particles or for any secondary separation to occur between the modules and electrode plates. The limited coagulation time increases the need for the residence time in the foam removal apparatus and the clarifier in order to allow for the formation of coagulated floc and its subsequent increase in size and density. The designing of a waste water treatment system to allow for more or less residence time in batch tanks and clarifiers is very difficult.
In previous electrocoagulation processes, including tubular modules as described in U.S. Pat. Nos. 4,293,400 and 4,378,276 to Liggett, improved removal rates have been shown. The improvements were due to the pre-alignment effect of passing the water to be treated through the electronegative or electropositive backside of the electrodes. These methods served to align the contaminant molecules and ions in the waste stream and made them more susceptible to react as the electrical current or electromotive force was introduced into the waste stream. This electrochemical phenomena is further enhanced by the subject invention by the application of reversing polarity of the direct electrical current current, which provides the electromotive force to drive the electrochemical reaction.
In U.S. Pat. No. 5,587,057 to Metzler et al., an electrocoagulation process is described having electrodes for treating a highly conductive liquid. In U.S. Pat. No. 6,613,202 to Herbst et al. and U.S. Pat. Nos. 5,043,050, 5,423,962, 6,179,977, 6,241,861 and 6,746,593 to Herbst, the inventor of the subject invention, Robert J. Herbst describes different types of improved electrolytic and electrochemical water treatment processes for treating aqueous solutions using conductive conduits and precipitating various organic and inorganic materials suspended in the solution.
None of the above mentioned prior art electrolytic and electrochemical systems and processes for treating waste water disclose the unique features of the subject invention which provides for treating large volumes of complex and variable waste water with reliability and functionality not obtainable with other electrocoagulation batch tank water treatment systems and processes.